ANAT: Back Flashcards
structure of vertebral column
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 4 coccygeal
functions of vertebral column
- protects spinal cord and spinal nerves
- support body weight
- provides a partly rigid and flexible axis for the body and a pivot for the head
- posture and movement
what are A, B, C, D?
- A = pedicle
- B = vertebral foramen
- C = articular processes
- D = spinous process
what are E, F, G, H?
- E = lamina
- F = transverse process
- G = vertebral arch
- H = vertebral body
explain the articulations of vertebrae
- 1) superior articular processes of one vertebra articulate w/ the inferior articular processes of the next (facet), allows for ROTATION
- 2) vertebral body articulates w/ the next vertebral body via intervertebral disc
how are cervical vertebrae arranged?
- C1 - atlas
- C2 - axis
- C3-6 (typical)
- C7 - vertebra prominens (long, slender spine)
structure of C1 (atlas)
- vertebral body
- spinous process
- foramen
- vertebral arches
- superior articulation
- atypical b/c lack of vertebral body and spinous process
- largest vertebral foramen
- contains TWO vertebral arches (A/P - each contains an A/P tubercle), other vertebrae have one
- articulates superiorly w/ occipital condyle of cranium
structure of C2 (axis)
- ANTERIOR tooth-like/odontoid process (dens) which projects superiorly and articulates w/ articular facets of atlas
what ligaments bind to the dens?
- cruciform (vertical and transverse ligaments): provide stability and prevent posterior displacement
- transverse ligament specifically binds the dens to the anterior arch of atlas
- apical: no functional significance but points tip of dens anteriorly
4 reference lines in the spine
what does a frontal X-ray with the patient’s mouth open show?
- the dens (odontoid) process of the axis (C2)
- therefore called odontoid view
structure of C3-C7
- vertebral body
- vertebral foramen
- transverse processes
- articular processes
- spinous process
- body: small, oval-shaped
- foramen: large, triangular
- transverse processes: contain transverse foramina
- articular processes: oblique and horizontal orientation
- spinous processes: short and bifid (except C7 - vertebra prominens)
structure of thoracic vertebra
- vertebral body
- vertebral foramen
- transverse processes
- articular processes
- spinous process
- body: large, heart-shaped
- foramen: small, circular
- transverse processes: long and contain facets for ribs (T1-T8 have superior and inferior costal facets, T9-T12 have only one costal facet)
- articular processes: almost coronal
- spinous processes: long, point inferiorly
structure of lumbar vertebrae
- vertebral body
- vertebral foramen
- transverse processes
- articular processes
- spinous process
- body: largest (since bear most weight), kidney-shaped
- foramen: triangular, larger than thoracic but smaller than cervical
- transverse processes: long, slender
- articular processes: almost sagittal
- spinous processes: short, sturdy
what type of vertebra is this?
cervical
what type of vertebra is this?
thoracic
what type of vertebra is this?
lumbar
structure of sacrum
- 5 bones fused into one wedge-shaped, immobile bone
- fusing finished by age 25-30
- provides strength + stability to pelvis and transmits weight of body to pelvic girdle via sacroiliac joint
- rough surface dorsally, smooth concave surface ventrally
what are A, B, C, D?
- A = sacral hiatus
- B = medial sacral crest
- C = auricular surface (forms sacroiliac joint)
- D = sacral canal
what are E, F, G?
- E = superior articular process (articulates w/ inferior articular process of L5)
- F = sacral foramina
- G = base
what are H, I, J?
- H = sacral ala (anterosuperior)
- I = transverse ridges/lines
- J = apex
structure of coccyx
- vestigal tail w/ 3-5 fused segments (very variable)
- has 2 horns which articulate w/ sacrum
- apex points anteriorly in males and inferiorly in females
spina bifida + types
- failure of vertebral lamina to unite during development, can be caused by folate deficiency
- mildest: spina bifida occulta (vertebral arch of L5 and S1 do not form completely, skin usually covers this but marked by tuft of hair or dimple, causes back pain and limb weakness)
- more severe: meningocele (fluid filled sac, no nerve damage but minor disability
- most severe: meningomyocele (spinal cord and nerves protrude thru > paralysis or weakness of limbs + bladder/bowel dysfunction)
curves of the vertebral column and how do they form?
- cervical (2˚) - lordosis
- thoracic (1˚) - kyphosis
- lumbar (2˚) - lordosis
- sacral (1˚) - kyphosis
- primary/kyphotic curves form during foetal development
- secondary/lordotic curves develop during childhood due to lifting head and upright sitting
3 types of vertebral column disorders
- kyphosis
- lordosis
- scoliosis
kyphosis + causes
- exaggerated thoracic curve (posterior)
- causes: osteoporosis, neuromuscular disorders,
lordosis + causes
- excessive anterior curve of lumbar region
- causes: obesity, pregnancy, abdominal muscle weakness
scoliosis + causes
- lateral curvature of column
- causes: unilateral muscular paralysis
how is the female lumbar spine different from males?
- during pregnancy, centre of gravity shifts anteriorly = disrupt posture and walking
- therefore more flexible to cope w/ carrying baby while standing on 2 feet
structure and function of intervertebral discs
- fibrous hyaline cartilage between vertebrae
- nucleus pulposus (avascular): soft, gelatinous inner sphere made of water - shock absorption + flexibility
- annulus fibrosus: outer collar of ligaments and fibrocartilage - resist compressive stress + provide protection
2 types of joints in the vertebral column
- vertebral body joints (where the discs are)
- facet joints (plane - b/n facets of vertebrae) - (zygapophyseal, allow for rotation)
4 ligaments of the facet (zygapophyseal) joints
- interspinous ligaments: connect spinous processes
- ligamentum flavum: connects lamina
- supraspinous ligament (most posterior): connects tips of spinous processes from C7 down (one continuous ligament)
- ligamentum nuchae: supraspinous ligament that connects tips of spinous processes from C7 up (one continuous ligament)
2 ligaments of the vertebral body joints + structure and function
- anterior longitudinal ligament (most anterior): thick, prevents hyperextension
- posterior longitudinal ligament: thin, prevents hyperflexion
osteoporosis + X-ray findings + causes
- decreased bone mass w/o changing shape
- X-ray shows striations on vertebra due to decreased horizontal trabecular bone and increased vertical stress
- causes: malnutrition, low physical activity, low oestrogen
describe the changes in the vertebral column during ageing
- articular surfaces curve inward = increased curvature = decreased height
- osteoporosis
- loss of fluid from intervertebral discs = become drier and thinner = compression = decreased height
movements of vertebral column
- flexion (bend forward)
- extension (bend backwards)
- lateral flexion (bend to one side, essentially adduction)
- lateral extension (bend back to midline, essentially abduction)
- rotation (cervical and thoracic)
facets orientation and movements throughout the vertebral column
- Atlanto-occipital: convex (occipital) and concave (atlas) - flexion/extension
- atlantoaxial: almost transverse = rotation
- C2-C7: oblique = all
- thoracic: almost coronal = limited rotation
- lumbar: almost sagittal = all except rotation
organisation of back muscles
- intrinsic (axial - originate and insert on vertebral column): superficial, intermediate, deep
- extrinsic (axio-appendicular - don’t originate or insert on vertebral column): superficial, intermediate
superficial extrinsic back muscles
- trapezius
- latissimus dorsi
- levator scapulae
- rhomboids major and minor
what is A?
- origin
- insertion
- innervation
- function
- trapezius
- origin: occipital bone and C7-T12 vertebrae
- insertion: lateral clavicle, acromion and spine of scapula
- innervation: spinal accessory nerve
- function: elevate scapula (superior/descending part), retract scapula (middle part), depress scapula (inferior part)
what is B?
- origin
- insertion
- innervation
- movements
- levator scapulae
- origin: transverse processes of C1-C4
- insertion: medial border of scapula
- innervation: dorsal scapular and cervical nerves
- movement: elevation of scapula
what is C and D?
- origin
- insertion
- innervation
- function
- C = rhomboids major
- D = rhomboids minor
- origin: dorsal surface of cervical and thoracic vertebrae
- insertion: medial border of scapula
- innervation: dorsal scapular nerve
- function: retract and rotate scapula
what is E?
- origin
- insertion
- innervation
- function
- latissimus dorsi
- origin: spinous processes of thoracic and lumbar vertebrae
- insertion: bicipital groove (humerus)
- innervation: thoracodorsal nerve
- function: extension, adduction, internal rotation of upper limbs
what is in the extrinsic intermediate layer
- serratus posterior
what is F?
- function
- innervation
- serratus posterior
- function: elevation of ribs 2-5 (superior) and depression of ribs 9-12 (inferior)
- innervation: 2-5th intercostal nerves and anterior rami to T9-T12 thoracic spinal nerves
which muscles form the superficial INTRINSIC layer
- splenius capitis
- splenius cervicis
what is A?
- origin
- insertion
- function
- splenius capitis
- origin: spinous processes of cervical and thoracic vertebrae
- insertion: mastoid process of occipital bone
- function: neck extension (when combined w/ splenius cervicis), lateral flexion, rotation
what is B?
- origin
- insertion
- function
- splenius cervicis
- origin: spinous processes of T3-6
- insertion: transverse processes of C1-C3/4
- function: neck extension (when combined w/ splenius capitis), lateral flexion, rotation
what muscles are in the intermediate intrinsic layer of the back
- erector spinae (spinalis, iliocostalis, longissimus)
what are A, B and C and what are their functions?
- A = iliocostalis (lateral column)
- B = longissimus (intermediate column)
- C = spinalis (medial column)
- erector spinae
- when acting unilaterally, lateral flexion
- when acting bilaterally, extension of spine + head
which muscles form the deep intrinsic layer?
- TRANSVERSOSPINALIS
- semispinalis (capitis, cervicis, thoracis)
- multifidi
- rotatores
what is A?
- what are its parts?
- function
- semispinalis (most superficial)
- 3 parts: capitis, cervicis, thoracis
- function: extension (bilateral) and contralateral rotation of head and vertebral column (unilateral)
what is B and C and what is their function?
- B = multifidi
- C = rotatores (deepest)
- stabilise vertebral column
which nerve innervates all intrinsic back muscles?
- posterior rami of spinal nerves
which muscles are involved in extension of the vertebral column?
- splenius
- erector spinae (spinalis, longissimus, iliocostalis): when they act bilaterally
- semispinalis
which muscles are involved in rotation of the vertebral column?
- multifidus
- rotatores
- internal and external obliques
- rectus abdominis
which muscles are involved in lateral flexion of the vertebral column?
- latissimus dorsi
- splenius
- erector spinae (spinalis, longissimus, iliocostalis) - when they act unilaterally
describe the arterial supply of the back
- vertebral arteries arise from the subclavian artery
- they travel thru the transverse cervical foramina
- anterior and posterior (x2) spinal arteries branch out from vertebral arteries, supplying spinal cord
describe the venous supply of the back
- vertebral column drained by internal and external vertebral plexus
- these drain into the spinal veins (3 anterior and 3 posterior)
- veins are valveless > blood can flow in both directions
describe the meninges
- dura mater: tough, thick, separated from inner walls of vertebral canal by epidural space
- arachnoid mater: avascular, CSF found in subarachnoid space
- pia mater: thin, transparent, vascular, covers spinal cord + neurovasculature
which muscles are responsible for flexing the back from an extended position?
- rectus abdominis
- psoas major
which muscles are responsible for extending the back from a flexed position?
- glutes maximus
(think RDL)
lumbar puncture
- used to draw CSF from subarachnoid space
- L4/L5 level b/c spinal cord ends @ L1-L2
epidural
- injection of local anaesthetic into epidural space e.g. pregnancy
in a herniated disk, how to know which nerve root will be affected?
- cervical discs would impact the LOWER nerve
- thoracic and lumbar discs would impact the HIGHER nerve
spondylosis
- pain from degenerative spine conditions
ankylosing spondylitis
- autoimmune arthritis of vertebral joints
spondylolysis
- stress fracture through pars interarticularis
- similar to spondylolisthesis except not dislocated
spondylolisthesis
- anteriorly slipped vertebrae
- usually L5 slips over S1
- ‘scottie dog’ fracture
at which level does the spinal cord become conus medullaris?
- L2 (spinal cord tapers off to become conus medullaris)
- then spinal nerves form cauda equina
8 layers breached in a lumbar puncture
- skin
- subcutaneous fat
- supraspinous ligament (pop)
- interspinous ligament (pop)
- ligamentum flavum (pop)
- dura mater
- subdural space
- arachnoid mater
- puncture goes into subarachnoid space
4 stages of disc herniation
- degeneration/protrusion (incomplete): slight bulging of nucleus pulposus
- prolapse (incomplete): slight bulging of nucleus pulposus and therefore annulus fibrosis
- extrusion (complete): nucleus pulposus starts to escape from annulus fibrosus but not fully detached
- sequestration (complete): when nucleus pulposus is entirely detached from annulus fibrosus
cervical myotomes C2-C4
- C2 look at your shoe: cervical flexion
- C3 a fallen tree: cervical lateral flexion
- C4 I’m not sure: scapular elevation
baston’s plexus (internal vertebral plexus)
- valveless veins that run along the spinal cord
- valveless = bidirectional = cancer can spread from abdominopelvic/thoracic region to brain
- but it means that blood won’t pool around spinal cord and put pressure on it
Jefferson fracture
- fracture of the anterior and posterior vertebral arches of C1 (atlas)
- poses risk to vertebral arteries
- caused by increased load e.g. diving headfirst into shallow water
hangman’s fracture
- fracture of pars interarticularis (area b/n superior and inferior articular processes) of C2 vertebra (axis)
- poses risk to spinal cord
- due to hyperextension e.g. MVA or hanging
which part of the spinal column can undergo AVN?
- dens (C2)
what is arthrodesis surgery?
- fusing a slipped vertebra to the one above so it doesn’t move
cauda equina syndrome
- compression of cauda equina (below L2)
- leads to paralysis, loss of sensation and bowel/bladder control
- e.g. due to disc herniation > MRI is skipped and we do surgery immediately
